Dying diffusa

I think my prized brigg/diffusa, Amigo, may be dying. When I left for class this morning at about 9:00am, she was on the bottom in her shell, which isn't uncommon for her in the least. I came back from class today at 2:00pm and she was still in the same spot, which was odd. I fished her out and then checked for a heartbeat, which I couldn't see. Next, I pulled on her operculum, which I noticed was extremely flimsy. This is def. not normal. I think the water chemistry at my college is very different and I had been so busy that I didn't notice that she wasn't getting enough calcium. I rushed to the store and got a cuttle bone and put it in the tank, but I fear I might be too late . The other brigg in there is just fine. I will be devastated if I lose her. I have a bunch of her babies at home, so I guess I could always keep one of those, but it just won't be the same . I checked over her shell and there aren't any grooves that go through her shell, but her trapdoor is pretty much destroyed and pond snails keep climbing on the inside of it. Am I too late?

She's still floating at the surface but she is still alive. She doesn't have her operculum closed tightly but she does close it if you touch her foot.

She died last night. My best guess would be rapid aging. The other snail in the tank is just fine and his operculum is in great shape.

" If the snail is not in optimal condition, this tissue is retracted and only the center of the opreculum is covered by snail tissue. In such cases one needs to check the water quality and make sure everything is allright. Old snails can show such tissue retraction as well, while it's not necessairly a real problem with them."

I found out this information about her condition. She has always been given the best care possible and her water quality is excellent. There was an incident though where I bumped the heater in the tank when she was about nickle size. The rest of the tank inhabitants died but she survived. Afterwards she would through a HUGE growth spurt so my guess is she aged quite a bit. I'm devastated though since she was my first snail ever. I'm sure gonna miss her.

R.I.P Amigo

I do put in fertilizers about once a month for the plants but it hasn't ever seemed to effect the snails at all. I do feed snail jello regularly when I'm home and when I'm at college I steal fresh veggies from the campus cafeteria to feed them (I wash them thoroughly first). There is no salt added to the tank and I make sure not to put anything in there that may have salt in it. I use AquaSafe water conditioner every time I add water. I do have detritus in the tank. I used to have planaria but I haven't seen any for a while.